The proposed research aims to investigate the child's early intellectual development in three closely related sets of studies: The first study is an in-depth longitudinal study of language comprehension in the child before and during the period when he is starting to talk. The proposed study concerns the development of comprehension of verbs which designate various actions and relations, and of sentences involving those verbs. The development of comprehension of particular terms for actions has not yet been systematically investigated, in part because the techniques which have been used thus far in the study of comprehension are not adequate for such an investigation. We propose to assess comprehension using brief films which directly portray ongoing events, having children choose the event appropriate to a particular description from two contrasting films. The second series of studies is designed to evaluate the effects of prosodic features of speech on language processing in very young children. While informal evidence suggests that exaggerated stress and slow speech are important to small children's comprehension, systematic data are lacking. We propose to assess the effects of speech rate, pause, and stress in comprehension and sentence memory tasks. The third series of studies is designed to investigate children's conceptualization independently of their ability to use language. We have developed tasks involving matching of different category instances which can be used with children as young as 1 1/2 years. We propose to examine the child's categorization of objects, spatial relations and actions, and to examine the relation between such categorization and the acquisition of lexical elements which designate those categories.